feat: add create and edit book form

Claude-Session: https://claude.ai/code/session_01M9MLit5Ko3X4s7rzC5Kv7X

src/App.tsx

@@ -6,6 +6,7 @@ import { LoginForm } from './auth/LoginForm'
 import { RequireAuth } from './auth/RequireAuth'
 import { BookList } from './books/BookList'
 import { BookDetail } from './books/BookDetail'
+import { BookForm } from './books/BookForm'
 import { secondaryButton } from './ui'
 
 export function App() {
@@ -25,6 +26,8 @@ export function AppRoutes() {
       <Route element={<RequireAuth />}>
         <Route element={<Shell />}>
           <Route path="/books" element={<BookList />} />
+          <Route path="/books/new" element={<BookForm />} />
+          <Route path="/books/:id/edit" element={<BookForm />} />
           <Route path="/books/:id" element={<BookDetail />} />
         </Route>
       </Route>